(CNN) -- With the Tuesday night shooting deaths of two students from the University of Texas in Ciudad Juarez, Mexico, six U.S. citizens have been killed in the volatile region this week, according to the U.S. consul general.

"We offer our deepest condolences to the families of victims. These incidences underscore U.S. travel warnings for Mexico," Consul General Dean J. Haas told CNN. "The current warning is clear and states that U.S. citizens should defer unnecessary travel to Juarez and areas near the Mexican border."

The current travel warning for U.S. citizens posted on the State Department website states, "Recent violent attacks and persistent security concerns have prompted the U.S. Embassy to urge U.S. citizens to defer unnecessary travel to Michoacán and Tamaulipas, to parts of Chihuahua, Sinaloa, Durango, and Coahuila, and to advise U.S. citizens residing or traveling in those areas to exercise extreme caution."

The consulate, based in Ciudad Juarez, would not comment on the extent of U.S. involvement in the investigation of the U.S. citizens killed in Mexico or their effect on relations with Mexico.

"Mexican authorities are in charge of this investigation," Haas said. "The U.S. government is engaged on a broad bilateral basis on a variety of issues, including law enforcement, with the Mexican government."

Violence is commonplace near the nations' border as powerful drug cartels battle for control of lucrative smuggling routes into the United States.

"We encourage U.S. citizens traveling in this area to register with the consulate. We have a mechanism to communicate travel updates of registered citizens within the state of Chihuahua," Haas said.

According to Haas, 108 U.S. citizens have been killed in the consular district of Chihuahua since October 1, 2009.

Lorena Izaguirre died of multiple gunshot wounds outside a tortilla shop on Saturday.

In a separate incident on Saturday, Jovana Herrera and Luis Carlos Araiza where shot while driving a BMW near the Zaragoza International Bridge.

Edgar Lopez died outside a house in Ciudad Juarez of multiple gunshot wounds, authorities said.

On Tuesday, University of Texas at El Paso students Manuel Acosta Villalobos, 25, and Eder Diaz Sotero, 23, were gunned down in a hail of more than 30 bullets while driving in Chihuahua State, Mexico.